1. Field of the Invention
The invention generally relates to systems that are configured to receive audio signals and play them back to a user.
2. Background
Many conventional consumer electronic devices provide a user with the ability to switch between multiple input audio sources, each of which may have a different audio signal level. Such devices may include but are not limited to television sets, cable set-top boxes, satellite set-top boxes, and preamplifiers and receivers in home stereo systems or home theater systems. If, after switching the input audio source, a difference between the signal level of the previous input audio source and the new input audio source is not compensated for, the user may be required to manually adjust the volume at which the output audio signal is played back. This can be a nuisance if such switching is frequent. A similar issue also arises for devices that allow a user to switch between different television channels, each of which may have a different audio signal level.
Consumers may also be annoyed by television commercials that are considerably louder than regular television shows. When such a commercial is aired, a user may be compelled to manually adjust the volume of their television set or cable/satellite set-top box to minimize a difference in loudness between the commercial and the television show.
What is needed, then, is a technique for automatically adjusting the volume, or magnitude, of an audio signal. The desired technique should be applicable to reduce a difference in signal levels between two different input audio sources, between two different television channels, and/or between a television program and a commercial.